Nozzle plate holding device for spinning of continuous filaments

ABSTRACT

A nozzle package is connected at its lower end to a heating box by means of elements which permit a good heat transfer to the nozzle plate included in the nozzle package.

FIELD OF THE INVENTION

The invention relates to a nozzle plate holding device and to a spinningbeam for melt spinning of continuous filaments, especially ofthermoplastic material (melt). The spinning beam comprises, for example,a heating box into which extend melt lines, melt pumps and nozzle pots(also called "nozzle packages") ending in nozzle plates. The nozzle potsmay form vertically turned-in portions of the heating box and may beattached in bell-shaped receptacles having a vertical, central meltconduit which runs into a melt inlet of the nozzle pots. The nozzleplate holding device forms a part of a nozzle pot.

DISCUSSION OF PRIOR ART

During melt spinning the temperature management of the melt from theextruder to the discharge from the spinning nozzle is of utmostimportance. Particular attention has to be paid that the melt has thesame thermal history for all filaments as regards to temperature anddwell time. Minor deviations of, e.g. only 2° C., may already lead tovisible dyeing differences or increased capillary breakage rates. Inorder to ensure a constant temperature the product lines and thespinning beams are presently usually condensation-heated. Condensationheating allows very precise temperature management because with thisprinciple primarily those spots of the room impinged with saturatedsteam can be heated intensively which have a lower temperature than thecondensation temperature of the saturated steam. This results in a veryeven temperature distribution at the condensation surfaces. Hence, thisheating principle permits accurate temperature control of the entiremelt distribution system to the degree while employing relatively simplemeans.

In the area of the melt discharge this is somewhat more problematical,however. Prior to the discharge of the filaments from the spinningnozzles another filtration and homogenization of the melt takes place inthe nozzle packages. These have to be removed from the spinning beamsfor cleaning purposes or when resetting the product for a differentnumber of filaments. Assembly and disassembly of the nozzle packagesshould be as simple as possible in order to restrict the work thereforto a minimum. For this reason the saturated steam cannot circulatedirectly around the nozzle packages. Therefore, the heat supply to thenozzle packages takes place only via heat conduction at the contactsurfaces between the nozzle package and the spinning beam as well as bythe supplied melt. On the other hand, however, the heat loss to theenvironment at the nozzle plates is extremely high, because they cannotbe insulated. This means that primarily in the area important forfilament formation an exact temperature management is particularlydifficult. Therefore, a closer study of this area is absolutelynecessary, especially because there has been and still is a trend tofiner filaments for which the melt flow through the nozzle package, andconsequently also an important heat supply, decreases.

The requirements concerning transmission of heat, or evenness oftemperature, have been known for a long time and have been clearlyformulated also in patent literature, see e.g. U.S. Pat. No. 4,437,827,in which heaters provided especially therefor were proposed to solvethis problem. The efforts connected therewith are considerable. Ifhowever the otherwise lacking heat has to be supplied along via the meltit may be necessary to increase the melt temperature which would resultin a loss in quality.

At the same time a nozzle package, however, must meet many otherrequirements. It should e.g.:

be easy to replace,

require no extraordinary process tolerances during manufacture,

create a sufficient sealing effect against melt leakage.

In case of a round nozzle package it should additionally be adjustablein a predefined angle position around a vertical axis in order to ensureproper arrangement of each fibril in the space below the nozzle. Theprevious attempts to meet these demands have led to a variety ofproposals and practical embodiments of which only a few examples shallbe listed below.

In most cases the connection with a carrier in the spinning beam is madeon the upper (inner) end of the nozzle package (see e.g. DE-C-1246221,DE-A-1660697, and U.S. Pat. No. 4,696,633). This will be the case evenif the package has to be introduced into the receptacle providedtherefor from the top or from the side (e.g. according to U.S. Pat. No.3,655,314, or U.S. Pat. No. 3,891,379).

It is known to attach the nozzle package via a flange to the lower endwith screws--see, e.g., U.S. Pat. No. 4,494,921. However, the attachmentmeans is used in said example to create the required sealing forces (bycompressing a packing ring at the upper end of the package). Therefore,an air gap remains between the flange and the carrier (the heating box).

It has even been proposed to provide "support strips"0 in a rectangularpackage such "that via metallic heat contact between the side walls ofthe heating box and the side walls of the spinning head, good heattransmission takes place from the heating box to the spinning head suchthat practically no temperature differences exist between the two"(EP-B-271801). This object however cannot be taken seriously as will beshown in the subsequent explanations of the present invention. Theapplication of such ideas in connection with a round nozzle package hasnot been proposed as of yet.

A "good heat transmission" based on the surface pressure of the nozzleplate holding device and a carrier is to be achieved also according toDE-C-1529819. It requires however a special formation of the carrierwhich impedes an effective heating of this part.

A known spinning beam is e.g. described in DE-Gbm 84 07 945. In thisspinning beam the receptacle for the nozzle pot (the nozzle package) iswelded into the heating box and hence practically a part of the heatingbox. The arrangement of the nozzle pot in the receptacle is providedsuch that a layering, consisting of nozzle plate, filter housing andnozzle pot bottom, is screwed to the bottom of the receptacle by meansof bolts which penetrate the layering and which are screwed into aninternal screw thread in the bottom of the receptacle. For example, inorder to remove the nozzle pot together with its components from thereceptacle for necessary cleaning, the screws must be loosened and thenthe nozzle pot can be pulled vertically downwards and out of thereceptacle. Given that the nozzle pots require frequent cleaning, attimes daily, which depends on the material to be processed, there is aconsiderable wear of the bolts in the area of the internal screw threadin the bottom of the receptacle. Here the bolts must be tightenedstrongly on account of the pressures of about 120-350 bar commonlyexisting in the nozzle pot which must be effected with a dynamometrickey in order to avoid damage to the bolts and the thread. Normally, atleast four bolts are required for attaching a nozzle pot so that thereresults a considerable amount of required work for each cleaning of thenozzle pot.

A different arrangement of a nozzle pot in a receptacle in connectionwith a spinning beam is known from the European Patent Publication 163248 (see especially FIGS. 3 and 6). In this embodiment the nozzle pothas a hollow cylinder which carries the nozzle plate by means of aninwardly reaching step on which nozzle plate the filter housing issupported over a circulatory joint. Above the filter housing an axiallymovable piston having a central passage hole is mounted in the hollowcylinder which is supported via a membrane in the form of an up sidedown dish over the dish edge with the nozzle pot empty. In case ofpressurized filling of the nozzle pot a gap between the filter housingand the membrane is filled with melt which presses the membrane awayacross a cross-section practically corresponding to the piston cylinderand hence presses the piston away from the filter housing. In thismovement the piston stroke is limited by a packing ring surrounding thecentral opening which packing ring rests against a ring nut which isattached via bolts to a pump block that is rigidly arranged in theheating box. The hollow cylinder is screwed with an inner thread ontothe ring nut, which is provided with an outer thread, by way of whichthe nozzle pot which is supported by the step of the hollow cylinder isattached to the heating box. To remove the nozzle pot the hollowcylinder is to be screwed off from the ring nut. The thread and themembrane of this arrangement are subject to a very considerable load,because the sealing membrane, which extends over the entirecross-section of the inner space of the hollow cylinder, and the threadare burdened by a force determined by the pressure and saidcross-section which may amount up to 15 t due to the relatively largecross-section of the inner space of the hollow cylinder. Hence, due tothe arrangement of the thread in the area of the bottom of thereceptacle there results for the filter pot a necessary free ring spacebetween the outer surface of the hollow cylinder and the opposite wallof the heating box, because the screwing-in and screwing-out of thehollow cylinder requires a certain play. This results in a heat transferfrom the corresponding wall of the heating box to the hollow cylinderwhich is interrupted by the ring space primarily in its area in which itcarries with its step the nozzle plate so that the required continuoussufficient heating of the nozzle plate is rendered more difficult.

SUMMARY OF THE INVENTION

Therefore, it is the object of the invention to facilitate, especiallyto speed up, the assembly and disassembly of the nozzle pots with areduced load on the sealing.

This is achieved according to the invention on the one hand in that thereceptacles are provided in the area of the nozzle plates with inwardlyreaching shoulders which are confronted with corresponding rests on thenozzle pots in such manner that the nozzle pots can be screwed into thereceptacles, the shoulders and the rests locking the nozzle pots axiallyinto the receptacle when in contact, on the other that between the meltinflow of the nozzle pots and the bottom of the receptacles gaskets areplaced so that the melt flowing into the nozzle pots sealingly pressesthe gaskets against the bottom of the receptacles and an inner edge ofthe nozzle pots while leaving a passage hole for the melt.

By way of this formation there results a continuous heat transfer fromthe inwardly turned receptacle in the heating box to the nozzle pot inthe area of the nozzle plates due to the there inwardly reachingshoulders, i.e., via the contact between the shoulders and the restsarranged on the nozzle pots so that the nozzle pot and hence the nozzleplate arranged directly in it are supplied in a sufficient and favorablemanner with the necessary heat. Due to the positioning of the gasketsagainst the inner wall of the nozzle pots there remains only arelatively limited movement range for the gaskets which corresponds tothe surface in the direct area of the passage hole so that thecorresponding area of the packing ring does not have to sustainconsiderable large forces.

Advantageously the gaskets are designed bell-shaped with a centralpassage hole, in assembled state they rest with their bottomssurrounding the passage hole on the bottom of the receptacles, and theouter edges of the gaskets rest on a ring shoulder in the nozzle pot.Due to this formation of the gaskets, when filling the nozzle pot, underthe pressure of the melt they press on the one hand against the bottomof the receptacle, this way the sealing effect between the nozzle pot inthe area of the central passage hole of the gasket and the bottom of thereceptacle automatically adapt to the corresponding prevailing pressure.

The nozzle pots are advantageously designed so that in a hollow cylinderof the nozzle pot the nozzle plate, a filter housing and above it a ringnut forming the nozzle pot floor with central opening are layered, thehollow cylinder carrying the nozzle plate with a step and the ring nutbeing screwed into an internal screw thread of the hollow cylinder whilepressing together the layered components, the nut shoulder pressing thegasket arranged on the filter housing against a conical inner surface ofthe ring nut in such manner that the gasket slightly protrudes from thecentral opening of the ring nut with its area surrounding the passagehole.

On account of this formation the gasket receives a centering through theconical inner surface of the ring nut so that after assembly of thenozzle pot it can be attached in the receptacle with proper position ofthe packing ring by way of the above mentioned bayonet lock. The gasketthen immediately presses into its right position against the bottom ofthe receptacle, the nozzle pot being sealed and prepared to being filledwith the material to be processed.

For the formation of a sealing between the filter housing and the nozzleplate the filter housing is advantageously designed so that in assembledcondition of the nozzle pot the filter housing sits with a cylindricalprojection on the nozzle plate and the projection surrounds aring-shaped recess in the filter housing into which the packing ring isplaced.

After completed assembly of the nozzle pot and after putting it underpressure, the cylindrical projection on the filter housing rests againstthe nozzle plate, this way the ring-shaped recess within the projectionformed by the projection is limited to the height of this projection.The packing ring placed into the recess cannot be excessivelycompressed. The sealing effect of the packing ring is determined hereautomatically by the pressure prevailing in the nozzle pot, because thispressure presses the packing ring outwardly against the projection andautomatically closes a possible gap between the projection and theopposite surface of the nozzle plate. The projection furthermore offersthe advantage that with it the entire height of the nozzle pot is alsodetermined, which therefore has a defined size when assembled.

Advantageously the shoulders arranged on the receptacles and the restsprovided on the nozzle pots are designed according to a bayonet lock.This results in a connection between the nozzle pot and the receptaclethat is extremely easy to open and close, i.e., simply by a turn of max.about 90°. Correspondingly, at the bayonet lock practically no wearappears even if the nozzle pot is removed frequently.

Advantageously, the formation of the receptacles with the inwardlyreaching shoulders which are faced by corresponding rests on the nozzlepot, and the arrangement of the gaskets that are supported on thebottoms of the receptacles can be used in combination, both measuressupplementing each other for a quicker and safer assembly anddisassembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail based on the Figures of thedrawings, wherein:

FIG. 1 shows schematically the heat flows at a nozzle package,

FIG. 2 shows a model of the package that has been formed according tothe finite element theory,

FIG. 3 shows schematically the temperature distribution in a nozzlepackage of conventional construction,

FIG. 4 shows schematically the temperature distribution in a nozzlepackage which is designed according to this invention,

FIG. 5 shows an embodiment of the invention,

FIG. 6 shows in a diagram the experimental result concerning the heat-upbehaviour of the spinning nozzles in the spinning beam withoutpolymer(melt), and

FIGS. 7A and 7B show a schematic representation of the conditions in thearea of the melt supply.

Heat Balance of the Nozzle Package

FIG. A chows the heat flows at a nozzle package.

A carrier is shown with the reference number 50 and the nozzle packagewith 52. The carrier 50 is part of a heating box which today is normallyheated with diphyl steam (e.g. according to DE-Gbm 09313586.6 from 7Sep. 1993). The package is received in a receptacle (the "nozzlecavity") 54 in the carrier. The package 52 comprises especially a nozzleplate 56 and a holding device 58. The holding device 58 has a hollow 60which contains further elements of the package as is described belowbased on FIG. 5. These elements are superfluous for the schematicrepresentation of the heat balance according to FIG. 1, however, and arenot described in detail in connection with the Figure. The essentialheat flows in FIG. 1 are shown as follows:

arrow 1: heat flow into the nozzle package through the entering melt

arrow 2: heat flow into the nozzle package through contact with thecavity

arrow 3: heat flow into the nozzle package through the air gap

arrow 4: heat flow from the nozzle package through the exiting melt

arrow 5: heat flow from the nozzle package through the heat radiation ofthe nozzle plate.

Due to the process the melt makes up for the largest part of heat supplyas well as carrying-off heat. Ideally, both heat flows are equal inamounts. This would mean that the melt maintains a constant temperatureuntil it discharges from the nozzle. In order to guarantee this, theother heat flows would have to be in balance. Special difficulties arehere created by the heat losses of the nozzle plate. Given that itcannot be insulated, a large part of the heat amount is given off to theenvironment in form of radiation and convection. This heat amount mustnow be guided as far as possible from the spinning beam via the nozzlepackage to the nozzle plate in order to reduce the cooling-off of themelt to a minimum.

With nozzle packages of conventional construction this heat supply takesplace exclusively from the top. The reason for this is the sealing ofthe nozzle packages. In order to guarantee that no melt exits laterallynext to the nozzle package they are pressed tightly against a gasket onthe top. By way of this compression a good thermal bridge is createdwhich however is located on the side opposite to the nozzle plate. Alsoin embodiments which are attached with a flange to the bottom of thespinning beam a possible additional heat flow through the lower flangeis to be neglected, because here an air gap is located between theflange and the spinning beam. The thermal conduction value of airhowever is lower than that of the nozzle package and the spinning beamby the factor 1 000. Even with an air gap of only 1/10 mm the possibleheat flow is negligibly low, because this supply is over-compensated bythe enlargement of the radiating surface in connection thereto.

FEM-Calculations

It is possible to calculate the heat distribution within the nozzlepackage and the nozzle cavity with the help of the finite element method(FEM). Given that in studies of the heat flow it is of primary interesthow the heating through the actual device components takes place,calculations without melt have been made which led to the modelaccording to FIG. 2. The temperature difference to the diphyltemperature hereby represents a measure for the heat amount that isextracted from the melt. In order to compensate a temperature differenceof 10° C. without polymer of the nozzle plate in comparison to the melt,the melt is cooled in production by an average of about 0.5° C.depending on the polymer, the nozzle diameter and the throughput.

For the calculations it is supposed that the heating box as well as thenozzle package have a homogeneous heat conduction capability. Given thatthe surface pressure of the parts in contact of cavity and nozzlepackage is relatively high, calculation at these transfers is done withthe same heat conduction capability. The spaces between nozzle packageand cavity that are filled with air are very small so that a movement ofthe air can be excluded. It can be assumed that the heat transportthrough the air gap takes place exclusively via heat conduction. Thefinite element model of nozzle cavity and nozzle package shown in FIG. 2is created. At the borders of the model various heat transfercoefficients as well as ambient temperatures can be employed. This waythe heat transfers by way of steam condensation, fluid heat carrier,radiation to the exterior and heat conduction in the insulation is takeninto consideration. With the given boundary conditions the temperaturedistribution in stationary state can be calculated and shown with theFEM-program.

FIG. 3 shows the temperature distribution in the nozzle package with anozzle diameter of 90 mm calculated this way. A temperature difference(Δ9) of about 30° C. has been calculated between the diphyl steam roomand nozzle plate. Depending on constructional embodiment (air gap,wall-thickness, etc.) this value can also vary by several degrees.Measurements at the pilot plant confirm the result of thesecalculations. This means that to equalize this temperature differencethe melt is extracted such an amount of heat that it cools off by about1.5° C. by the time it exits from the nozzle. This temperaturedifference however is not to be viewed as constant over all nozzles.Rather, it may vary strongly if the conditions of heat conductionchange. Contamination in the nozzle cavity, e.g., can form thermalbridges and hence considerably influence an even heat supply to thenozzle plate. Therefore, this temperature difference represents ameasure for the accuracy of the temperature management of the melt atthe nozzle discharge, this being of great importance especially withvery fine filaments. Measurements at nozzle plates in production plantsconfirm that with nozzle packages of conventional construction thespreading of the temperatures is within a range of 2° C.

In order to estimate also the influences of constructional featuresseveral dimensions have been varied and the temperature distributionshave been determined. An enlargement of the heat transfer surface on topof the nozzle package, e.g., by using a larger sealing, showedpractically no influence on the temperature of the nozzle plate. Evenwith a contact of the entire upper surface of the nozzle package withthe cavity merely yields a temperature increase of max. 1° to 2° C. Onaccount of the appearing gradient this influence is negligibly low. Thereason for this are on the one hand the relatively long heat conductionpaths from the upper side of the nozzle package to the nozzle plate. Onthe other hand the heat flow is restricted by the narrowestcross-section of the conductor of heat which is essentially predefinedby the wall-thickness of the nozzle package.

Improvement of the Heat Flow Into the Nozzle Plate

Based on the analyses of the heat flow a new nozzle package has beendeveloped in which the heat conduction paths from the diphyl steam roomto the nozzle plate have been greatly shortened. The object of thismeasure is an improved heat compensation at the nozzle plate. Therefore,in the preferred embodiment of this solution a bayonet lock has beenattached at the height of the nozzle plate. This way additional heatconduction paths have been created which enable a heat flow as close aspossible to the place of heat loss.

In order to design this heat supply as large as possible, changes arerequired at the spinning beam as well. Therefore, it is important thatthe condensation surface is as large as possible, especially at thelower side of the nozzle cavity. It must be assured that a sufficientheat amount is available for the temperature compensation of the nozzleplate. If this is not the case even the opposite effect can be achievedin that the heat is not supplied to the nozzle plate but carried offfrom it. In the construction of the spinning beam, e.g., two measurescan be implemented which have been described in the German registeredutility patent no. 9313586.6. On the one hand the interior of theheating box is so designed such that the diphyl flows off immediatelyand hence no liquid swamp forms in the cavity area. Furthermore, for theenlargement of the condensation surface ribs are attached to the nozzlecavity. This way a sufficient heat supply to the nozzle package isguaranteed. The result of this construction can be seen in FIG. 4. Thetemperature gradient of diphyl steam room to nozzle plate could reducedaccording to the finite element calculations by about 10° C. to 20° C.This is an improvement of the temperature management of about 30% ascompared to the conventional construction.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 5 shows a section of a spinning beam with a nozzle package(especially of a nozzle plate holding device) according to thisinvention. The spinning beam comprises a heating box 1, into whichextend melt lines and melt pumps (not shown), as shown, e.g., in theFigures of the above-mentioned DE-Gmb 84 07 945. In the heating box 1the receptacle 2 is inserted, e.g., by way of welding, which consists ofthe wall 3 which is concluded towards the interior by the bottom 4. Thereceptacle 2 encloses the cylindrical inner space 5 into which thenozzle pot 6 is inserted. For this purpose the inner space 5 passes overto the outer room via the cylindrical opening 7. The bottom 4 ispenetrated by the melt conduit 8 which is connected to a melt pump (notshown).

The nozzle pot 6 is a rotation body, and it is shown in the Figure insection like the receptacle 2. The nozzle pot 6 consists of layeredcomponents, i. e., of the nozzle plate 9, the filter housing 10 and thethread nut 11. These three components are placed into the hollowcylinder 12 which carries with its step 13 the nozzle plate 9. On theside of the thread nut 11 the hollow cylinder 12 is provided with theinner thread 14 into which the thread nut 11 is screwed in with itsouter thread 15. To screw the thread nut 11 into the hollow cylinder 12,the thread nut 11 is arranged with the pocket holes 16 and 17 into whicha matching sickle spanner fits. The screwing-in of the thread nut 11into the hollow cylinder 12 is limited by the cylindrical projection 18at the side of the filter housing 10 facing the nozzle plate 9. Onceduring screwing-in of the thread nut 11 the projection 18 rests on thesurface 19 of the nozzle plate 9, the entire length of the nozzle pot 6is determined. Within the cylindrical projection 18 a ring-shaped recessis present which is filled by the packing ring 20. The packing ring 20is pressed towards the outside against the cylindrical projection 18 bythe pressure of a material to be processed which for this fills out theintermediate space 21 between the surface 19 and the bottom surface 22of the filter housing 10, and this way with the effect of this pressurea sealing adapted to the pressure results automatically between thefilter housing 10 and the nozzle plate 9.

The hollow cylinder 12, which as component of the nozzle pot 6 carrieswith its step 13 the nozzle plate, is itself retained in the receptacle2, i.e., by means of the shoulder 23 which is faced in the shownbuilt-in condition by the supports 24 on the hollow cylinder 12. Theshoulders 23 form components of the insert pieces 25 which are insertedinto the wall 3 of the receptacle 2 and which are tightly screwedtogether with the wall 3, i.e., by means of bolts 26. The shoulders 23and the supports 24 together form a bayonet lock which axially locks thenozzle pot 6. Simultaneously, the bayonet lock forms a direct thermalbridge via the shoulders 23 and the supports 24 via which the nozzleplate 9 is directly heated. By turning the hollow cylinder 12 and henceby turning the nozzle pot 6 by about 90°, the connection between thereceptacle 2 and the nozzle pot 6 is released. The nozzle pot 6 can thenbe removed from the receptacle 2 through the cylindrical opening 7 anddisassembled into its parts, e.g., for cleaning purposes of the filterhousing 10 and of the nozzle plate 9.

When inserting the nozzle pot 6 into the receptacle 2 the gasket 27,which is placed essentially in a conical embodiment in the thread nut11, becomes effective and said thread nut has a conical inner surface 28for the reception of the gasket 27. The gasket 27 rests with its outeredge 29 on the ring-shoulder 30, which is part of the melt distributor31 resting on the filter housing 10. This melt distributor 31 is here acomponent of the nozzle pot 6, it serves to distribute the melt suppliedthrough the melt conduit 8 within the interior of the nozzle potfavorably, which will be described in detail below.

In assembled condition of the nozzle pot 6 the gasket 27 is supported,as mentioned, the ring shoulder 30, this way it extends verticallytowards the top into the bottom 32, which surrounds the passage hole 33that is in alignment with the melt conduit 8, while being in contactwith the conical inner surface 28 of the thread nut 11.

As the figure shows the bottom 32 of the gasket 27 slightly protrudes asopposed to the surface 34 of the thread ring 11 so that when closing thebayonet lock 24/25 the bottom 32 rests tightly on the bottom surface 35of the bottom 4 of the receptacle 2. This way the sealing is createdbetween the bottom 4 of the receptacle 2, which is penetrated by themelt conduit 8, to the nozzle pot 6, i.e., while taking advantage of thepressure prevailing in the interior of the nozzle pot 6 which pressesthe gasket 27 against the bottom surface 35 and the conical innersurface 28 of the thread nut 11 depending on how high the pressure is.Furthermore, the gasket 27 is pressed radially outwardly against thepoint of impact 36 between the thread nut 11 and the filter housing 10so that here too a safe sealing is created.

During operation the melt flow takes place as follows: the melt flowsfrom the melt conduit 8 through the passage hole 33 to the meltdistributor 31 which is overflowed by the melt and which reaches theconduits 37 of which conduits only two are shown. In the shownembodiment about 24 such conduits are present. The melt then flowsthrough the filter 38 which towards the bottom is concluded by the grid39. Furthermore, in the filter housing 10 the conduits 40 are arranged(about 50 such conduits are present) from where the melt flows into theintermediate space 21. Now the melt flows through the nozzle plate 9,i.e., through the bores 41 which end in capillaries in the lowerlimitation surface 42 of the nozzle plate 9. Here the filaments exitsingly which are then comprised to form single threads.

For the verification of the theoretical studies temperature measurementsat the spinning beam have also been made. A spinning beam has beenmodified in such manner that a nozzle package of conventionalconstruction as well as the new nozzle package according to FIG. 5("Quick Fit") could be employed side by side. By way of thisexperimental arrangement influences which go beyond the differences ofconstruction could be excluded to a large extent. For the experiment thespinning beam was heated to a diphyl temperature of 290° C.Subsequently, the two nozzle packages were employed cold (about 20° C.)and the temperature was measured at the nozzle border and nozzle center.FIG. 6 shows the result of this experiment.

In FIG. 6 the dashed curve A represents the heat-up behaviour(temperature course over a time after the assembly into the spinningbeam - without polymer) of a conventional nozzle package in the nozzlecenter, while the dashed curve B shows the corresponding behaviour inthe border part of a conventional package. Curve C shows the heat-upbehaviour in the nozzle center of a package according to this invention(e.g. according to FIG. 5), while curve D (which coincides to a largeextent with curve C) shows the heat-up behaviour of the border part ofthe new package.

The new nozzle package with the improved heat flow clearly reaches thefinal temperature earlier than the nozzle package of conventionalconstruction. Furthermore, the final temperature of the new nozzlepackage is about 10° C. higher, which corresponds to the calculations.The temperature difference between the nozzle center and the nozzleborder already is negligibly low with the nozzle package of conventionalconstruction, however with the new nozzle package it could be improvedby the last nuance. Hence, the experiment confirms the calculatedresults, according to which the cooling-off of the melt in the newnozzle package is about 0.5° C. lower than with the nozzle package ofconventional construction. This value seems to be quite small but is ofmajor importance for the quality of the produced yarn especially in themanufacture of microfilaments.

FIG. 7A shows "optimum" conditions in the area of the melt supply in the"nozzle cavity", i.e. in the receptacle in the heating box whichaccommodates the nozzle package. The receptacle itself has an axialsurface 100 which is directed in the spinning direction. This surfacefaces a front face 102 of the nozzle package after the package is in itsoperating condition, a gap 104 being present inbetween. The distancebetween the front face 102 and the contact surfaces of the receptaclecan be determined during the manufacture or assembly (i.e. duringconstruction) of the package without having to consider themanufacturing tolerances of the heating boxes.

A flexible insulation lip 106 extends out from the upper end of thepackage in order to touch the surface 100. The hardness, flexuralstrength, and dimensions of the flexible lip have been chosen such thatthe surface-to-surface contact according to FIG. 7A is created. Ideally,the lip adjusts to unevenness of the surface 102.

The risk of a leakage between the lip and the surface 102 is small uponfirst entrance of the melt through the admission conduit, because themelt pressure is low, until the chamber in the package below the lip hasbeen filled. Until this has occurred the lip is pressed additionallyagainst the surface 102 by the melt, this counteracts the risk of aleakage.

The contact conditions prior to the entrance of the melt are importantas is intended to be shown by the faulty design according to FIG. 7B.Here the elasticity of the lip has been chosen too great. Therefore, thelip edge bends towards the bottom again which leaves open a wedge gapbetween the edge and the surface 102. This yields a surface of attackfor the entering melt which may lead to a "peeling off" of the lip fromthe surface 102 and lead to a leakage. Of course, a leakage can also beformed in that the elasticity, which presses the lip against the surface102, is chosen too low so that the entering melt can penetrate into theremaining gap between the lip and the surface 102.

The lip is provided on a sealing body which is "embedded" in the packageso that the body is supported against the melt pressure by the packageand only the lip must deform under the melt pressure. Preferably, thelip forms one piece with the body. Advantageously, the body can beformed, or arranged, in such manner that it can accept additionalsealing functions in the package itself.

The sealing element (the lip) can be plastically deformable underoperating pressure, the element then having to be replaced prior to arenewed insertion after removing the package from the cavity. Thematerial of the element however can be chosen so that the element can beelastically deformable and hence reusable also under the operatingpressure, e.g., if a chrome steel is used. When reinserting the package(prior to the entering of the melt) the sealing is preferablyelastically deformable.

The sealing element (the sealing lip and the sealing body) are exposedto the melt during operation. Therefore, a sealing material must bechosen that will not react with the melt. A metal is preferred, aluminumand steel being suited in most cases. A sealing according to FIG. 5(with a lip and a body part consisting of one piece), in which theconical body part is in contact with a conical support surface in thepackage, can be shaped, e.g. by a deep-draw method or by metal stamping.A sheet thickness of up to about 3 mm (e.g. for steel about 1 mm and foraluminum 1.5 to 2 mm) is employable.

Preferably, the package is provided with a limit stop which determinesin the operating position of the package its angle position around avertical axis. This way the arrangement of the bore in the nozzle platecan be predefined towards the cooling duct. Where the connection to thecarrier is effected via a bayonet lock, at least one element of the lockcan exert the function of the limit stop.

A multiple bayonet lock could be used, this may require measures inorder to distribute the surface pressure over the rests of the lock.Normally, this will require tighter manufacturing tolerances. Given thatthe radial dimension of these rests strongly influences the division(the mutual distance) of the packages in the spinning beam, thisdimension should be maintained as small as possible because a minimaldivision is generally desirable. The radial distance between the jacketsurface of the package and the outer end of each rest is preferably notgreater than 10 mm. In case of a multiple lock this dimension can bemaintained smaller than 5 mm. Preferably no more than three rests arepresent per thread.

The invention in its first aspect (connection at the lower end of thepackage) yields as short as possible flow paths for the heat between theheating box and the nozzle plate. This aspect of the invention is notrestricted to the employment in combination with a sealing lip, eventhough, preferably it is employed in combination with a sealing whichdevelops its full sealing effect through the melt pressure. Suchsealings are also known, e.g., from U.S. Pat. No.4,645,444.

The new sealing type itself is of advantage, independent from theconnection between the nozzle package and the heating box - it canreplace, e.g., the piston sealing according to DE-C-12 46 221 or DE-C-1529 819 or U.S. Pat. No. 4,696,633.

In FIG. 5 the cylindrical jacket surface of the nozzle package is shownwith M. This surface must have a somewhat smaller diameter than theinterior surface of the nozzle cavity in order to enable theproblem-free insertion of the package into the cavity. The distance Abetween the bottom side of the rests and the more distant front face ofthe package is chosen somewhat smaller than the depth of the cavity inorder to ensure the insertion of the package without contact with theend surfaces of the cavity. The radial dimension of the rest is shownwith D.

The concept of a connection at the lower end of the package naturallyrequires the corresponding formation of the lower end of the nozzlecavity. This can take place with the formation of the heating boxitself, but preferably a carrier frame for the package is designedseparately and is attached to the heating box, e.g., by means of screws,as shown in FIG. 5. Preferably, the frame is replaceable, i.e., theattachment means can be loosened Without destroying parts.

We claim:
 1. A holder for a nozzle plate for continuous filamentspinning apparatus, said holder comprising a hollow, generallycylindrical, body provided with an upwardly facing, radially extending,step on its inner surface for supporting the periphery of the nozzleplate; means for cooperating with said body for clamping the nozzleplate against said step; and diametrically opposed supports projectingradially outwardly from the outer cylindrical surface of said body forattachment by a bayonette connection to a spinning beam.
 2. A holder asclaimed in claim 1, wherein said holder has a melt inlet and is providedwith a sealing member which surrounds the inlet.
 3. A holder as claimedin claim 2, wherein the sealing member has a flexible lip which iselastically deformable under the melt pressure.
 4. A holder as claimedin claim 3, wherein said lip is provided on a part that is against themelt pressure.
 5. Apparatus for spinning continuous filaments comprisinga spinning beam; a nozzle assembly removably fixed to said spinningbeam; and a gasket between said spinning beam and said nozzle assembly;said nozzle assembly including a hollow generally cylindrical bodyhaving an internal step, a nozzle plate having a radially protrudingportion resting on said step, a filter component resting on said nozzleplate, means cooperating with said cylindrical body for holding saidfilter component in place on said nozzle plate, said last-mentionedmeans having a central opening at a top portion thereof through whichmelt may pass downwardly to said filter component and having anoutwardly and downwardly flaring internal surface coaxial with andadjacent to said central opening, and diametrically opposed radialprojections from the outer surface of said cylindrical body at a lowerend portion thereof; said spinning beam having a generally cylindricalreceptacle portion for receiving said body, a horizontal wall at theupper end of said receptacle portion provided with a melt inlet openingin alignment with said central opening, and diametrically opposedinwardly projecting shoulders adjacent the lower end of said receptacleportion in position to cooperate with said radial projections from saidcylindrical body to provide a bayonette lock for removably holding saidnozzle assembly in said receptacle portion of said spinning beam. 6.Apparatus as claimed in claim 5, wherein said gasket has a centralpassage hole, is bell-shaped, and in its assembled condition has theedge portion thereof adjacent said central passage hole in contact withsaid horizontal wall at the upper end of said receptacle portion and theouter edge of the gasket in contact with a portion of the nozzleassembly.
 7. Apparatus for melt spinning continuous filaments comprisinga heating box including a plurality of upwardly extending bell-shapedreceptacle portions with substantially vertical central axes, each ofsaid receptacle portions having an upper wall provided with an axialmelt inlet opening; a nozzle package positioned in each of saidreceptacle portions and having a nozzle plate at the lower end thereof;said heating box being provided with inwardly projecting shoulders onopposite sides of the lower end of each of said receptacle portions; andsaid nozzle packages each having outward projections positioned tocontact said shoulders to axially lock said nozzle packages in saidreceptacle portions when, said packages are screwed into saidreceptacles.
 8. Apparatus for melt spinning continuous filamentscomprising a heating box including a plurality of upwardly extendingbell-shaped receptacle portions with substantially vertical centralaxes, each of said receptacle portions having an upper wall providedwith an axial melt inlet opening; a nozzle package positioned in each ofsaid receptacle portions and having a nozzle plate at the lower endthereof; and nozzle gaskets positioned between the bottoms of the upperwalls of said receptacle portions and the adjacent nozzle package in amanner so that melt flowing into the nozzle packages presses saidgaskets against the bottoms of the upper walls of the receptacleportions and against inner edges of the nozzle packages while leavingopen passages through which the melt may flow toward said nozzle plates.